Go here for all the details: http://puzzle-gis.codehaus.org/
The site asks itself the question why there is a need for a GIS application, since so many already exist. The answers provided are as follows:
That, in a nutshell, sums up the reasons why Java is cool and why the NetBeans Platform makes perfect sense. Pluggability of the application might have been added as a motivation as well, though if distribution is going to be via Java Web Start, chances are that the application providers will want to keep control over the installation themselves.
Here are a couple of inspiring pictures (click to enlarge them) to show you where all this is headed:
Of course, a next step is to ask the project owners for an interview and to see if they'd like a screenshot of their cool application to be added to the NetBeans Platform Showcase. So watch this space.